Thermal relay



Sept; 15, 1925. 1,553,405

B. H. SMlTH THERMAL RELAY Filed Feb. 26. 1921 WITNESSES: INVENTOR 2 21 4914 W fiei jam/h /7; 5/77/1/7. BY

i 4 ATTORNEY Patented Sept. TE, 1925.,

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BENJAMIN E. SMITH, 0F WILKINSBURG', EENHSYLVAIZTIA, ASSIGNOR TU WESTING- HOUSE ELEQTRIC & MANUFACTURING. CQMPANY, A CORPORATION OF PENNSYL- Valera.

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To all whom it may concern:

Be it known that T, BENJAMIN H. SMITH, a citizen of the United States, and a resident of Wilkinsbur in the county of Allegheny and State of ennsylvania, have invented 'a new and useful Improvement in Thermal Relays, of which the following is a specification. v

My invention relates to relays and particularly to thermal relays of the cartridge One object of my invention is to provide a thermal relay that shall have sufiicient time interval in. the operation thereof to effect protection of electrical apparatus from overloads.

Another object of my invention is to pro vide a thermal relay that shall embody means for reinforcing the same to effectively maintain the co-operating portions of the relayin alinement.

Another object ofmy invention is to provide a thermal relay in which a time-element shall be obtained in the operation thereof by causing current to traverse a portion of the bimetallic member and permitting another portion thereor" to move freely in accordance with the temperature condition thereof developed by the heat conducted thereto trom the current-conducting portion. 1 7

Another object of my invention is to provide a relay, out the above indicated char acter, that shall be adapted'for use in. car-v tridge-fuse clips and be reliable and efi'ective in its operationi In practising my invention, I provide a bimetallic member that-embodies a relatively wide base portion and a relatively narrow portion that extends therefromand is free to move. The base portion of the bimetallic member is heated by the current traversing the same, and the narrow portion, of the bimetallic member isheated by the heat con ducted thereto from the relatively wide base portion.

.The narrow portion of the member, when heated to a predetermined degree, is adapted to engage or be disengaged from a stationary contact member, according to the design of rela employ d.

The sing e figure of the accompanying drawings is a diagrammatic View of an electrical circuit and a perspective view,

with parts broken away, of a relay, embodymg my invention, that is connected the circuit.

An electrical translating device 1 is connected to an electrical circuit 2 that is provided with-an interrupter 3 for disconnecting the same when the device 1 attains a dangerous temperature. The interrupt-er 3 drical casing 7 of insulating material, two

metallic ferrules 8 and 9, blade terminal members 8a and 9a, a tubular metallic conductlng member 10, an adjustable contact member 11 and a bimetallic member 12 upon which a contact member 13 is mounted.

The tubular member 10 is slotted, at the one end, to receive the blade 8a and is slotted at the other end to receive a relatively wide base portion 14 of the bimetallic member 12. r

The base portion 14 of the bimetallic mem ber is secured between the tubular member 10 and the blade 9a to form a substantially rigid structure. A relatively narrow portion 15 ofthebimetallic member 12 extends inwardly from the relatively wide base pormounted on, and supported by but insulated justable member '11 may be so adjusted that the bimetallic member 12 will normally maintain engagement between the contact member 13 and the contact member 11 until a predetermined temperature has beenfiat tained by the bimetallic member.

The relay is so connected in the circuit 2 as to be traversed by the current traversing the circuit. The circuit current traverses the blade 9a, thebroad base portion 14 of the bimetallic member 12, the tubular conduct ing member 10, and the blade 8a. Thus, only lit) the base portion 1a of the bimetallic member is traversed by the circuit current. Heat is conducted from the base portion to the relatively narrow portion 15, causing the same to so expand as to effect the disengagement of the contact member 13 from the contact member 11.

Since the circuit energizing the electromagnet 4 is maintained by the effective engagement between the contact members 11 and 13, the consequent disengagement of those contact members, when the bimetallic member 12 becomes heated to a predetermined degree, de-energizes the electromagnet and permits the spring 5 to open the interrupter.

The disposition of the tubular member 10 around the bimetallic member 12 maintains a dead-air space therearound that prevents convection of heat from that member and serves to so heat lag the bimetallic member that it is caused to have either the same heating characteristic as the device to be protected or to require such time to operate that effective protection of the device 1 may be obtained.

The tubular member 10 serves the double purpose of supporting the bimetallic member 12 and electrically connecting the bi metallic member between the blade members thus avoiding the necessity of using auxiliary conductors which are usually a source of trouble in devices of this character.

The bimetallic member 12 comprisesv a plurality of relatively thin bimetallic elements secured together. A bimetallic member so constructed is more efficient and satisfactory in its operation than a similar member of corresponding size and currentcarrying capacity comprising but one relatively thick element, since the tendency for the element to set is obviated.

My invention is'n'ot limited to the specific structure that is illustrated, since it may be variously modified within the spirit and scope of the invention, as set forth in the ap pended claims.

I claim as my invention l. A thermal-responsive device comprising a cylindrical casing, two knife-blade members, a conducting member disposed within the casing and secured to one blade member, and a bimetallic member secured between the conducting member, and the pther blade member to form a rigid struc ure.

2. A thermal relay comprising a cylindrical casing, two knife-blade members, a conducting member disposed within the easing and secured to one blade member, a contact member extending through the casing, and a bimetallic member having a relatively wlde portion thereof secured between the conducting member and the other blade member to form a rigid structure and a relatively narrow portion thereof adapted to be actuated when heated to a predetermined degree to engage the contact member.

3. A thermal relay comprising a cylindrical casing, two knife-blade members, a conducting member disposed within the casing and scored to one blade member at one end thereof and slitted at the other end there of, a bimetallic member having a relatively wide portion securely disposed between the slitted portions of the conducting member and a relatively narrow portion extending along the conducting member, and a contact member controlled by the narrow portion of the bimetallic member in accordance with the temperature thereof.

4. A thermal relay comprising a cylindri cal casing, two knife-blade members therefor, a substantially rigid conducting member connected to one blade member and a bimetallic member connected tothe other blade member, the conducting member and the bimetallic member being connected to permit unimpeded movement of a portion of the bimetallic member in accordance with the temperature thereof.

5. A thermal relay for an electric circuit comprising a bimetallic element, one portion of which is traversed by the circuit current and a contact member that is controlled by another portion of the element.

6. A thermal relay for protecting an elec trical apparatus comprising a cylindrical metallic conducting member, a) bimetallic member having a relatively wide base portion secured to one end of the cylindrical conducting member and a relatively narrow portion extending within the cylindrical member, and a contact member controlled by the narrow portion of the bimetallic member.

7 A thermal relay comprising a metallic conducting member, a bimetallic member, one portion of which is connected in circuit with the metallic member, an enclosing casing and end contact members therefor, one of which is connected to the metallic member and the other of which is connected to the bimetallic member.

8. A thermal relay comprising a conducting member, a bimetallic member having one portion thereof secured to the conducting member and one portion adapted to be actuated when heated to a predetermined degree, a knife-blade member for the conducting member, a knife-blade member for the bimetallic member, a casing for enclosing the whole as a unit and a contact member extending through the casing and adapted to be en aged by the bimetallic member.

9. thermal relay for an electric circuit comprising a cylindrical casing, two knife-blade members therefor, a' conducting member secured to one blade member at one aeraeoe end thereof, a bimetallic member having one portion thereof securely connected between.

the other end of the conducting member and electrical circuit current comprising a bino metallic member having one portionthereof traversed by the circuit and another portion thereof freeto move in accordance with the heating developed therein by-the heat conducted thereto from the conducting portion thereof.

ll. A thermal relay for an electrical circuit comprising avbimetallic member having one portion thereof traversed by the circuit current and another .portion thereof free to move in accordance .with the heating developed therein by the heat conducted thereto from the conducting portion thereof, and a contact member controlled by the mov-v able portion of the bimetallic member 12. A thermal relay comprising a cylindrical insulating casing,- a cylindrical metallic conducting member extending therein, an adjustable contact member disposed through the casing, a bimetallic member having one portion thereof secured to one end of the metallic memb r, and the other end adjacent to and adapted to engage the contact member, a

mite-blade member dis osed at one endof the casing and secure to the conducting member and a second knife-blade member disposed atthe other end of the casing and secured to the bimetallic member.

13. A thermal relay for an electric cincuit comprising a bimetallic member havbig one portion thereof traversed by the circuit current and embodying a relatively large heat-storage capacity and a secondportion embodying a relatively small heatstorage capacity and adapted to. be heated by conduction from the current-conducting portion.

14. The method of obtaining a time-element in the operation of a bimetallic member which consists in causing current to traverse one portion of the bimetallic member and permitting another portion of the member to move" freely in-accordance with the heat conducted thereto from the currentconducting portion.

In testimony whereof, I have hereunto subscribed my name this 15th day of February, 1921. I BENJAMIN H. SMITH. 

